#include <bits/stdc++.h>
using namespace std;

#define int int64_t
#define endl "\n"
using PII = pair<int, int>;
using TII = tuple<int, int, int>;
#define FOR(i, a, b) for (int i = (int)(a); i <= (int)(b); i++)
#define FOR2(i, a, b, c) for (int i = (int)(a); i <= (int)(b); i += c)
#define FORD(i, b, a) for (int i = (int)(a); i >= (int)(b); i--)
#define FORD2(i, b, a, c) for (int i = (int)(a); i >= (int)(b); i -= c)
#define BSI basic_string<int>
#define BSPI basic_string<PII>
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define VI vector<int>
#define VII vector<vector<int>>
#define VPII vector<PII>
#define lowbit(x) ((x)&(-x))
#define RE return;
#define RET return true;
#define REF return false;
#define Yes cout << "Yes" << endl;
#define YES cout << "YES" << endl;
#define No cout << "No" << endl;
#define NO cout << "NO" << endl;
#define pb push_back
#define fi first
#define se second
#define sz size()
constexpr int N = 2e5 + 10;
constexpr int mod = 998244353;

int __FAST_IO__ = [](){
    ios::sync_with_stdio(0), cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(12);
    return 0;
}();

int n;

double get(double a,double b,double c,double d){
    return (a-c)*(a-c)+(b-d)*(b-d);
}

bool check(int x,int y){
    double t1=get(0,0,x+0.5,y+0.5);
    double t2=get(0,0,x+0.5,y-0.5);
    double t3=get(0,0,x-0.5,y+0.5);
    double t4=get(0,0,x-0.5,y-0.5);
    return !(t1<=n*n&&t2<=n*n&&t3<=n*n&&t4<=n*n);
}

void solve() {
    cin>>n;

    int ans=0;

    FOR(i,1,n){
        int l=-1,r=n;
        
        while(l+1!=r){
            int mid=l+r>>1;
            if(check(i,mid))r=mid;
            else l=mid;
        }
        // cout<<i<<' '<<r<<endl;
        ans+=r;
    }


    cout<<ans*4+1;
}

signed main() {
    int Task = 1;
    for (; Task; Task--) {
        solve();
    }
    return 0;
}